Improved utilisation of fossil fuel by injection through hollow electrodes in the EAF

Abstract

Tests at three furnaces of a new technology for injection of fossil fuel into the arcing zone of EAF show:

- at a plasma furnace:- -.an arc power increase (Vs. pure argon) when 6 % CH4 or 20 % CO2 or mixtures are added,-a very fast nitrogen removal, operating in an atmosphere of 95 % Ar + 5 % CH(4),-a hydrogen pick-up due to the methane injection that is quickly removed when the injection is stopped;

- at a 1 tonne pilot furnace:- - a power increase close to zero when N2 is injected,- - lower power when the gas injected is argon,- - a considerable power increase using propane or methane,- - high volatile coal powder injection generates a marked instability of the arc;

- at a 1 tonne DC furnace:- - a significant shortening of the electric arc length, using either methane or commercial gas or oil,- - a reduction of the electrode consumption,- - a chemical reduction of the slag; also involving silica.

They also show a denitrogenisation and desulfurisation of the steel.

Experiments indicate that proper measures must be taken, during hydrocarbon injection, to avoid clogging hole problems, due to the side deposition of native carbon coming from cracking. Tests lasting 2 hours or more, performed by means of a water-cooled lance that operates very close (less than 50 cm) to the electrode tip, show a way to overcome this problem.